In the early stage, a scanning apparatus is used to scan the image of a single paper. After the image of the paper has been scanned, the document should be removed from the scanning apparatus and then a next paper may be supported on the scanning apparatus in order to be further scanned. Since the process of manually replacing the paper is very troublesome, the conventional scanning apparatus is not feasible to scan a stack of papers. Recently, an automatic document feeder is integrated into the scanning apparatus. After a stack of papers to be scanned are supported on the input tray of the automatic document feeder, the automatic document feeder will successively transport the papers to perform a scanning operation without the need of manually replacing the papers. This means of automatically feeding the papers is both time-saving and efficient. In addition, the automatic document feeder is also feasible to perform a duplex scanning operation.
Generally, the paper feeding channel within the conventional automatic document feeder is specially designed. The height of the paper feeding channel is highly related to the friction force acting on the to-be-fed paper. As known, by elaborately determining the height of the paper feeding channel, the friction force acting on the to-be-fed paper is adjustable. In a case that a conventional automatic document feeder specially designed for feeding an ordinary paper with an ordinary thickness is used, when the ordinary paper is moved through the paper feeding channel, the friction force acting on the ordinary paper may allow the paper to be smoothly transported through the scanning region of the flatbed scanner in order to achieve good scanning quality. However, a thicker paper with a thickness greater than the ordinary thickness is difficultly transported through the paper feeding channel. Even if the thicker paper can be transported through the paper feeding channel, there are still some drawbacks. For example, since the friction force acting on the thicker paper is greater than the friction force acting on the ordinary, the scanning quality is deteriorated.
For solving these drawbacks, an automatic document feeder capable of adjusting the height of the paper feeding channel has been disclosed. FIG. 1 is a schematic side view illustrating a conventional automatic document feeder with a channel-height adjustable structure. As shown in FIG. 1, an automatic document feeder 10 is integrated into a flatbed scanner 11, and thus the automatic document feeder 10 and the flatbed scanner 11 collectively define an automatic sheetfed scanning apparatus 1. The automatic document feeder 10 comprises a feeder casing 101, an input tray 102, a pick-up roller assembly 103, a paper feeding channel 104, plural transfer roller assemblies 105, a channel adjusting module 106, a paper ejecting roller assembly 107 and an output tray 108. The flatbed scanner 11 comprises a scanner casing 111, a scanning platform 112 and a scanning module 113. The configurations and the functions of the flatbed scanner 11 are well known to those in the art, and are not redundantly described herein.
In the automatic document feeder 10, the input tray 102 is disposed on the feeder casing 101 for supporting a first paper P1 or a second paper P2. The first paper P1 has a first thickness T1. The second paper P2 has a second thickness T2. The second thickness T2 is greater than the first thickness T1. For example, the first thickness T1 of the first paper P1 is 0.15 mm, and the second thickness T2 of the second paper P2 is 0.3 mm. The pick-up roller assembly 103 is disposed beside the input tray 102 for feeding the first paper P1 or the second paper P2 that is supported on the input tray 102 into the paper feeding channel 104. The paper feeding channel 104 is disposed within the feeder casing 101. The first paper P1 or the second paper P2 may be transported through the paper feeding channel 104. As shown in FIG. 1, the paper feeding channel 104 has a first channel height H1. The plural transfer roller assemblies 105 are arranged in the paper feeding channel 104 for transporting the first paper P1 or the second paper P2. The paper ejecting roller assembly 107 is used for ejecting the first paper P1 or the second paper P2 to the output tray 108. The output tray 108 is used for supporting the first paper P1 or the second paper P2.
The channel adjusting module 106 is disposed within the feeder casing 101 for adjusting the channel height of the paper feeding channel 104. The channel adjusting module 106 comprises a channel adjusting roller 1061, a moving mechanism 1062 and a rotating mechanism 1063. The channel adjusting roller 1061 is used for contacting with the first paper P1 or the second paper P2, thereby transporting the first paper P1 or the second paper P2 through the paper feeding channel 104. The moving mechanism 1062 is connected with the channel adjusting roller 1061 for moving the channel adjusting roller 1061 upwardly or downwardly with respect to the paper feeding channel 104, thereby changing the channel height of the paper feeding channel 104. The rotating mechanism 1063 is connected with the channel adjusting roller 1061 for driving rotation of the channel adjusting roller 1061.1
Please refer to FIG. 1 again. For feeding the first paper P1 by the automatic document feeder 10, the first paper P1 supported on the input tray 102 is transported by the pick-up roller assembly 103 to be fed into the paper feeding channel 104. After the first paper P1 is fed into the paper feeding channel 104, the first paper P1 is transported by the plural transfer roller assemblies 105, so that the first paper P1 is moved in the paper feeding channel 104. When the first paper P1 is moved across the region over the scanning platform 112 and the scanning module 113, the first channel height H1 of the paper feeding channel 104 allows the first paper P1 to be smoothly scanned by the scanning module 113. Afterwards, the first paper P1 is transported to the output tray 108 by the transfer roller assemblies 105 and the paper ejecting roller assembly 107. Meanwhile, the task of scanning the first paper P1 is completed.
Whereas, for feeding the thicker second paper P2 by the automatic document feeder 10, the channel adjusting roller 1061 is moved by the moving mechanism 1062 of the channel adjusting module 106, so that the channel adjusting roller 1061 is moved upwardly with respect to the paper feeding channel 104. Under this circumstance, the channel height of the paper feeding channel 104 is changed to a second channel height H2, wherein the second channel height H2 is greater than the first channel height H1 (see FIG. 2). In such way, when the second paper P2 is transported through the paper feeding channel 104, the friction force acting on the second paper P2 may allow the second paper P2 to be smoothly scanned in order to achieve good scanning quality. The transporting process of the second paper P2 is similar to that of the first paper P1, and is not redundantly described herein.
Although the channel height of the paper feeding channel 104 of the conventional automatic document feeder 10 may be adjusted by the channel adjusting module 106, there are still some drawbacks. For example, since the moving mechanism 1062 of the channel adjusting module 106 occupies the space within the feeder casing 101, it is difficult to further reduce the volume of the automatic document feeder 10. Moreover, since the moving mechanism 1062 should be connected with a driving device (e.g. a motor), the loading of the automatic document feeder 10 is increased.